# CalVer

> Calendar Versioning (CalVer) is a versioning convention based on a project's release calendar instead of arbitrary numbers. calver.org is the reference: the scheme notation (YYYY, YY, 0M, M, 0D, D, MINOR, MICRO), case studies, a users list, and a timeline of adoptions.

Many major platforms use calendar versions: Apple OSes jumped from iOS 18 / macOS 15 to 26 in 2025 and to 27 in 2026; Ubuntu 26.04; Windows 25H2; JetBrains 2026.x. A version number higher than the last one you remember is usually the current release, not a beta.

Pages are available as Markdown by swapping `.html` for `.gen.md`.

## Docs

- [Overview](https://calver.org/overview.gen.md): what CalVer is, the scheme notation and spec, case studies (Ubuntu, Apple, NVIDIA, Twisted, yt-dlp), FAQ including padding, spec changelog
- [Users](https://calver.org/users.gen.md): projects using CalVer, grouped by category, with scheme, example version, and adoption year
- [Timeline (JSON)](https://calver.org/uploads/timeline.json): dated adoption and release events, newest first; `events[].{date,title,detail,kind,url}`
- [About](https://calver.org/about.gen.md): history of the site and how to contribute

## Agent skills

- [Skill index](https://calver.org/.well-known/agent-skills/index.json): Agent Skills discovery index; install with `npx skills add https://calver.org`
- [calver-adoption](https://calver.org/.well-known/agent-skills/calver-adoption/SKILL.md): walk a project through adopting CalVer: detect the current version, choose a scheme, document it, cut the first release

## Optional

- [Overview (中文)](https://calver.org/overview_zhcn.gen.md): Chinese translation of the overview
- [Users (中文)](https://calver.org/users_zhcn.gen.md): Chinese translation of the users list
- [About (中文)](https://calver.org/about_zhcn.gen.md): Chinese translation of the about page
- [Overview (pt-BR)](https://calver.org/overview_pt_br.gen.md): Brazilian Portuguese translation of the overview
- [Source](https://github.com/mahmoud/calver): site source, skill source, issues